Ben Creisler
bcreisler@gmail.com
A new online paper:
J.J. Hornung and M. Reich (2014)
Tylosaurine mosasaurs (Squamata) from the Late Cretaceous of northern Germany.
Netherlands Journal of Geosciences (advance online publication)
DOI: http://dx.doi.org/10.1017/njg.2014.31http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9440147&fulltextType=RA&fileId=S0016774614000316
Two genera of tylosaurine mosasaurs, Tylosaurus and Hainosaurus, are
recorded for the first time from Germany. Tylosaurus sp. is
represented by two isolated tooth crowns, originally described as
Mosasaurus? alseni (here considered a nomen dubium) from the latest
Santonian–Early Campanian, which are very similar to T. ivoensis and
T. gaudryi. The material of Hainosaurus sp. comprises a maxillary with
associated postorbitofrontal, two pterygoid teeth and several
indeterminate cranial fragments. The specimen from the Late Campanian
is slightly less derived than H. bernardi from the Maastrichtian in
retaining labiolingually less compressed anterior maxillary teeth and
unserrated pterygoid teeth with only very weak carinae. Despite only
minor skeletal differences, the genus Hainosaurus is considered to be
distinct from Tylosaurus because of its significant modification of
the dental apparatus compared to the plesiomorphic condition in the
latter. This dental morphology suggests a phylogenetic trend from a
generalised-piercing marginal dentition in Tylosaurus towards the
increasingly labiolingually compressed, symmetrical, strongly
bicarinate cutting marginal teeth in Hainosaurus spp. from the Early
through Late Campanian and Maastrichtian. A similar trend is also
present in pterygoid teeth with very indistinct unserrated carinae in
the Campanian Hainosaurus sp. towards serrated ones in the
Maastrichtian H. bernardi. A short review indicates the presence of
Hainosaurus in northern, central and western Europe (Sweden to Spain)
since the Early Campanian, and the occurrence of Tylosaurus spp. in
the same area until the Late Campanian. Hainosaurus persisted until
the end of the Maastrichtian; outside Europe it may have been present
in the Late Campanian of the USA and the Maastrichtian of the
Democratic Republic of Congo. Judging from a simple, uni- to
bicarinate, stoutly conical tooth morphology in aigialosaurs and very
basal mosasaurs as well as phylogenetic patterns, the development of
blade-like cutting tooth crowns appears to have been convergent in
several clades of large-bodied Campanian–Maastrichtian mosasaurids.
These include both mosasaurines ('Leiodon' mosasauroides,
Prognathodon? sectorius, Prognathodon? kianda, Eremiasaurus
heterodontus) and tylosaurines (Hainosaurus spp.).